JPH07113756A - Defect inspection method of color filter for view finder - Google Patents

Abstract

PURPOSE:To provide a defect inspection method by which almost the whole obverse and reverse surfaces of a color filter for a view finder can be inspected. CONSTITUTION:A color filter 3 for a view finder is held by a circular arc-shaped recessed part 7 of a transparent plate, and transmission illumination and/or reflection illumination are radiated to the color filter for the view finder, and a photograph is taken by an image pickup camera 1, and image processing is carried out on an obtained signal, and a defect is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual inspection method for a color filter used in a viewfinder.

[0002]

2. Description of the Related Art Conventionally, as a visual inspection method for a color filter for a viewfinder, a human visual inspection method using a light projector and a fine defect that is difficult to visually inspect are
The microscope method was adopted. However, in recent years, with regard to color filters for viewfinders,
Miniaturization and mass production have come to be demanded. With the increase in definition, even with regard to defects, it has become increasingly required to detect fine defects, and with regard to inspection with the naked eye using a conventional light projector or microscope, differences between people, Due to the problem of reproducibility, an automated inspection method that is not manual is required. In addition, automated inspection methods have been required for mass production. However, in the case of a color filter for a viewfinder, the entire front and back surfaces of the product are inspected, and it is necessary to inspect for defects with transmitted and reflected illumination on the entire front and back surface of the product. It was said that the fixing method was difficult. A method of sandwiching and fixing the side of the color filter for the viewfinder can be considered, but it is time-consuming and not suitable for mass production. Further, as shown in FIG. 5, it has been proposed to fix the color filter for the viewfinder only at the square portion, but in this method, the inspection cannot be performed sufficiently (fixed side) for the fixed regions at the four corners. Although there was a defect, in other areas, the defect can be detected by transillumination and / or reflective illumination on the front and back of the product. As described above, there has been a demand for an automatic inspection method capable of inspecting the entire front and back surfaces of a color filter for a viewfinder by using transmitted illumination and / or reflected illumination, which is suitable for mass production.

[0003]

Under such circumstances, the present invention provides an automatic appearance inspection method for a viewfinder color filter. More specifically, in the automatic inspection, a viewfinder color filter is provided. Hold the image so that it does not interfere with the imaging of the entire front and back surfaces, illuminate the viewfinder color filter with transmissive illumination and / or reflective illumination, image the front and back surfaces, and detect the defects by processing the resulting image signals. An automatic defect detection method is provided.

[0004]

A defect inspection method for a color filter for a viewfinder according to the present invention is obtained by irradiating a color filter for a viewfinder with transmitted illumination and / or reflected illumination and photographing with an image pickup means. An automatic inspection method for detecting a defect by image-processing a signal, in which a color filter for a viewfinder is held with a colored surface facing upward in an arc-shaped recess of a transparent plate. . As shown in FIG. 1 and FIG. 2, when the viewfinder color filter is held in the arc-shaped recess of the transparent plate, the contact point between the plate and the color filter is only the edge part of the color filter, and other than that. In the area, the two are separated.
Thereby, almost the entire area of the front and back of the color filter for the viewfinder can be photographed by the image pickup means including the CCD area sensor or the like by irradiating the transmitted illumination and / or the reflected illumination. Further, by doing so, almost all the front and back areas of the color filter for the viewfinder, which is the object to be inspected, are not in contact with other objects, so that no stains or scratches are generated on the front and back surfaces. .
The arc-shaped concave portion on the color filter side of the transparent holding plate is within a range where adverse effects on the inspection due to lens effects, interference, etc. are not significant.

Further, the defect inspection method of the present invention is to illuminate the color filter for the viewfinder from the side of the holding plate having the transparent arc-shaped recess with reflection dark-field illumination. By setting the colored side of the color filter for the viewfinder to the upper side and illuminating the reflected dark field with the transparent plate side,
It is possible to detect defects such as minute stains and scratches on the glass surface side of the color filter.

[0006]

According to the defect inspection method of the present invention, the color filter for the viewfinder is illuminated by the transmissive illumination and / or the reflective illumination, the color filter for the viewfinder is photographed by the image pickup means, and the obtained signal is image-processed. By doing so, it is possible to automatically inspect the front and back of the color filter, and by inspecting the color filter for the viewfinder while holding it in the arc-shaped recess of the transparent plate, almost all areas of the front and back of the color filter can be checked. It is capable of automatic inspection. Further, the inspection is performed while holding it in the arcuate recess of the transparent plate, so that no stain or scratch is generated on the front and back surfaces of the color filter at the time of the inspection. Further, by performing reflection dark field illumination on the transparent plate side, it is possible to detect minute stains and scratches on the glass surface of the color filter. After all, with such a structure, it is possible to provide an automatic appearance inspection method for a color filter for a viewfinder, which can be applied to miniaturization and mass production.

[0007]

Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of the automatic inspection apparatus in the first embodiment, in which the viewfinder color filter 3 is held by a transparent holding plate 4 having an arcuate recess on the glass surface side with the colored surface side up. In this state, the transparent holding plate 4 side transmits light by the light source 2a, and the colored surface of the color filter 3 reflects light by the light source 2b through the half mirror 6, and the image is taken by the image pickup camera 1 including a CCD area sensor. The processed image signal is processed by the image processing device 5. In the figure, 1 is an image pickup camera, 2a and 2b are light sources, 3 is a viewfinder color filter used in the first embodiment, 4 is a holding plate, 5 is an image processing device, and 6 is a half mirror. The image pickup camera 1 has a CCD area sensor, and the entire image surface of the viewfinder color filter 3 is imaged on the CCD area sensor through a lens. The light source 2a illuminates the entire surface of the viewfinder color filter 3, and the light source 2b reflects it by the half mirror 6 to illuminate the entire surface of the viewfinder color filter 3 by reflective brightfield illumination. The holding plate 4 is for holding the color filter 3, and the side holding the color filter 3 is formed with an arcuate concave portion, and since the color filter 3 is held in this portion, Filter 3
Is only the edge of the holding plate 4 on the glass surface side.
Contact with. Further, the holding plate 4 is a transparent plate, and it is possible to irradiate the entire front and back surfaces of the color filter 3 with the light source 2a. An enlarged view of the transparent holding plate 4 of the color filter 3 provided with arcuate recesses is shown in FIG. 3, and the one having a maximum distance of about 0.5 mm from the glass surface of the color filter was used. This is because the size of the color filter for the viewfinder is about 15 mm × 13 mm, so that the arc-shaped recess is formed in the holding plate 4 so that the adverse effect on the inspection due to the lens effect, interference, etc. is not significant. belongs to.

As the detection processing, a video signal photographed by the image pickup camera 1 illuminated by transmissive illumination and / or reflected illumination enters the image processing device 5 and is subjected to enhancement processing or the like to detect a defect. The image processing will be described with reference to FIG. 4 by taking an example. First, the same portion of the sample is imaged a plurality of times by the imaging means to obtain an image signal, and the obtained image signals for a plurality of times are integrated and averaged. This is because the light transmittance distribution as shown in FIG. 4A is obtained for the portion including the defective portion, but the video signal from the image pickup apparatus is as shown in FIG. Slow signal change (shading) due to uneven sensitivity and random noise generated in the video signal circuit,
And it corresponds to a signal that includes a local change of the signal due to dust adhering to the optical system, at the same location, imaged by the imaging means a plurality of times to obtain an image signal, The obtained image signals for a plurality of times are integrated and averaged. As a result, as shown in (c),
When the number of additions is N, the ratio of random noise is 1 / N ^1/2 . Here, A1, B1, A2, and B2 indicate defective portions, and C indicates a local change of a signal due to dust or the like attached to the optical system. Then, by slightly shifting the image pickup position and similarly performing integration and averaging, a signal (d) obtained by slightly displacing the signal (c) can be obtained. When the difference signal is obtained, it becomes as shown in (e), and the signal component that does not change due to the gradual signal change (shading) or the movement of the imaging position is removed. Here, only the signal component due to the change in light transmittance and the reduced random noise component remain, but when the signal (e) is further subjected to subtraction or differentiation of the neighborhood average value, , The gradual signal change (shading) component is also removed, and as a result,
It can be seen that in the obtained signal (f), only the portion corresponding to the defective portion locally changes and is emphasized. Regarding binarization by slice processing, the signal (f) is processed at a predetermined slice level SL, and only the defective portion is judged and binarized. The type of defect (white defect or black defect) can be identified by the order of signal inversion in the defect portion in FIG. In addition, here, the white defect refers to a pinhole or a pattern defect in the colored pattern portion, and the black defect refers to an extra colored portion or a light-shielded portion other than a predetermined pattern in the colored pattern portion, which causes stains or stains. Scratches on the glass part are also detected as black defects.

Next, a second embodiment will be described with reference to FIG. FIG. 2 is a view showing the arrangement of an automatic inspection apparatus according to the second embodiment, which is a color filter 1 for a viewfinder.
3 is held by a transparent holding plate 14 having an arcuate recess,
The transparent holding plate 14 side of the color filter 13 is reflected and dark-field illuminated by the ring-shaped light source 12, and the image processing device 15 processes an image signal captured by the imaging camera 11 including a CCD area sensor. The imaging camera 11 is
It has a CCD area sensor, and the entire surface of the image of the color filter 13 passes through a lens to form an image on the CCD area sensor. The light source 12 illuminates the entire surface of the viewfinder color filter 13 with reflection dark field. here,
A ring type fiber light source is used, but is not limited to this. The transparent holding plate having the arc-shaped recess used here is the same as that in Example 1, and the maximum distance between the transparent holding plate and the glass surface of the color filter is about 0.5 mm. Since the size of the filter is about 15 mm × 13 mm, the arc-shaped recess is formed in the holding plate 4 so that the adverse effect on the inspection due to the lens effect, interference, etc. is not significant. As in Example 1, color filter 1
Since only the edge portion of the glass surface 3 on the glass surface side comes into contact with the holding plate 14, almost the entire glass surface of the color filter 13 can be illuminated, and almost the entire glass surface can be photographed. Then, the glass surface side of the color filter 13 is illuminated by reflected dark field illumination, and defects such as fine dirt and scratches are detected without being affected by the holding plate 14 in almost the entire area of the glass surface side. It is possible. Further, during inspection, almost the entire area of the front and back of the color filter 3 does not come into contact with other parts, thereby preventing dust from adhering and scratching. As the detection process, a video signal captured by an image pickup camera with reflection dark field illumination enters an image processing apparatus, and an enhancement process or the like is performed in substantially the same manner as in the first embodiment to detect a defect. Since the optical axis of the dark-field light does not coincide with the optical axis of the light-receiving section of the image pickup means, almost all the diffracted light of the defective portion is detected as light due to dark-field illumination to the light-receiving section. The S / N becomes larger than that in the case of field illumination.

[0010]

With the above-mentioned structure, the defect inspection method of the present invention can provide an automatic appearance inspection method which can be applied to the miniaturization and mass production of color color filters for viewfinders.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an apparatus according to a second embodiment of the present invention.

FIG. 3 is an enlarged view of a holding plate portion according to the first embodiment of the present invention.

FIG. 4 is a diagram for explaining image processing in the embodiment of the present invention.

FIG. 5 is a holding view of a color filter for a viewfinder in a conventional defect inspection.

[Explanation of symbols]

1, 11 Imaging cameras 2a, 2b, 12 Light source 3, 13, 23 Viewfinder color filter 4, 14, 24 Holding plate 5, 15 Image processing device 6, 16 Half mirror 7, 17 Arc-shaped recess

Claims (2)

[Claims] 1. An automatic inspection method for detecting defects by irradiating a color filter for a viewfinder with transmissive illumination and / or reflective illumination, photographing with an imaging means, and image-processing the obtained signal. A defect inspection method characterized in that a color filter for a finder is inspected while being held in a circular arc-shaped recess of a transparent plate with a colored surface facing upward. 2. The defect inspection method according to claim 1, wherein the viewfinder color filter is illuminated by reflected dark field from the transparent plate side.